The invention relates to a device for holding and positioning an endoscopic instrument introduced through a body surface of a patient, with a holder for the instrument, which holder is designed in such a way that the instrument can be positioned relative to the body surface in different spatial tilt positions, which holder has a first bow-shaped element whose two end portions are arranged directed towards the body surface, and whose middle portion is directed away from the body surface, and which holder has a second bow-shaped element whose end portions are directed towards the body surface, but arranged offset by approximately 90° relative to the end portions of the first bow-shaped element, and whose middle portion is directed away from the body surface by substantially the same distance as the first bow-shaped element, and the instrument being guided at an overlapping region of the two bow-shaped elements.
A device of this kind is known from the document DE 94 15 039 U1.
A device of this kind is used in the context of minimally invasive surgery. In minimally invasive surgery, an instrument, which in the context of the present invention is understood as a working instrument such as scissors or forceps for tissue preparation and also as an endoscope, is introduced into the operating site via an incision in the body surface, in order to perform a surgical intervention under endoscopic visual control. The instrument is in this case usually introduced into the inside of the body via a trocar which is fitted into the incision.
Particularly if the instrument is an endoscope, it is sometimes necessary to position the endoscope in different tilt positions relative to the body surface in order to be able to inspect all areas of the operating site.
The positioning of the instrument or trocar has customarily been carried out by assistants. However, it would be desirable for simple manoeuvres such as positioning of the instrument to be taken over by a controllable holding and positioning device, which would mean less assistance was required and, in addition, would permit more exact positioning of the instrument.
Thus, it would be sensible if the endoscope, which carries the camera for video image recording, were to be held and guided via an endoscope holder and guidance system. Holding and positioning of an endoscope or instrument is possible, for example, with a device known from U.S. Pat. No. 4,573,452. This device has a selectively tensionable cable-type component which is released in order to move the endoscope, after which the endoscope can be brought manually into the desired position, and is then clamped to a rigid structure in order to fix the endoscope in the set position. A disadvantage of this known device is that the positioning, i.e. the changing of the position, of the endoscope can only be done manually.
Another manually adjustable holding and positioning system is known from U.S. Pat. No. 5,810,712 and has a holder in the form of a ring, with a ball mounted in the latter via a cardanic suspension and acting as a seat for the instrument. The ball of the cardanic suspension can be fixed in the desired tilt position.
However, motor-driven devices for holding and positioning of an instrument are also already known, for example from U.S. Pat. No. 5,184,601 or from U.S. Pat. No. 5,766,126. These devices not only make it possible to receive the endoscope and fix it in position, but also permit intracorporeal adjustment, during the operation, of the working instruments being used in said operation, either by direct control from outside or automatically by detection of the instrument tips in the image processing and by corresponding control of the guidance system, or by detection of the position and direction of the instruments via position sensors and by corresponding control of the holding and positioning device.
A disadvantage of these intelligent holding and positioning devices, however, is their complicated structure and in particular their overall size, which conceals a large area of the operating site. Moreover, these known devices are awkward to install and can only be cleaned with some difficulty. Because of their complicated structure and the use of sensitive components, these devices cannot be sterilized in an autoclave and, for hygiene purposes, they therefore need to be provided with a sterile foil cover during the operation. Moreover, these devices are expensive and, because of their heavy and solid design, they are generally not transportable, so that they cannot be used successively at different locations.
Because of these disadvantages, these known devices are not suitable for simple and brief minimally invasive procedures, because the installation and preparation times for these known devices are out of all proportion with the time needed for the operation.
The document DE 94 15 039 U1 mentioned at the outset describes a device for guiding surgical instruments, for example a trocar, where the two bow-shaped elements, at their two end portions, can be moved via rollers along a respective guide track shaped as a segment of a circle. This device, which is comparatively simple from the point of view of its construction, means that the instrument clamped with its shaft in the device is permitted the area of movement of a rectangular double pyramid whose tips pointing towards each other coincide at an invariant point lying on the shaft axis of the instrument, and both ends of the shaft move on a respective spherical sector surface, the centre points of these lying at the invariant point. However, guiding the two bow-shaped elements on curved guide tracks via rollers has various disadvantages.
Because of the curvature of the guide tracks, the frame of this device has a considerable overall height, which has the disadvantage that the invariant point of the instrument's movement lays far above the body surface. Moreover, it is difficult to provide the rollers with a motor drive if this is desired for automation of the instrument's positioning. Moreover, because of the guide rollers and guide tracks, this known device has a great many nooks and crannies in which it is possible for dirt to accumulate, which can be removed only with difficulty. Moreover, in this known device, it is necessary, because of the guide tracks, for the frame to be made rectangular, which requires a greater amount of space.
Furthermore, U.S. Pat. No. 5,330,485 discloses an instrument guidance device used for guiding instruments in brain surgery. This known device has two differently curved bow-shaped elements which are secured on a common pivot axis and can be pivoted about the latter. In this device, the instrument to be guided cannot be moved about an invariant point.
The object of the invention therefore is to make available a device, of the type mentioned in the introduction, which has an even simpler structure, can be set up quickly, and takes up the least possible space on the patient's body.